Today, very sad news has reached me: Atul Chitnis has
passed away. Most people outside of India will most likely not
recognize the name: He has been instrumental in pineering the BBS
community in India, and the founder and leader of the Linux Bangalore
and later FOSS.in
conferences, held annually in Bangalore.

I myself first met Atul about ten years ago, and had the honor of being
invited to speak at many of the conferences he was involved in. Besides
that professional connection, we became friends. The warmth and
affection with which I was accepted by him and his family during my many
trips to Bangalore is without comparison. I was treated and accepted
like a family member, despite just being this random free software
hacker from Germany who is always way too busy to return the amount of
kindness.

Despite the 17 year age difference, there was a connection between the
two of us. Not just the mutual respect for each others' work, but
something else. It might have been partially due to his German roots.
It might have been the similarities in our journey through technology.
We both started out in the BBS community with analog modems, we both
started to write DOS software in the past, before turning to Linux. We
both became heavily involved in mobile technology around the same time:
He during his work at Geodesic, I working for Openmoko. Only in recent
years his indulgence in Apple products was slightly irritating ;)

Only five weeks ago I had visited Atul. Given the state of his health,
it was clear that this might very well be the last time that we meet
each other. I'm sad that this now actually turned out to become the
thruth. It would have been great to meet again at the end of the year
(the typical FOSS.in schedule).

My heartfelt condolences to his family. Particularly to his wonderful
wife Shubha, his daughther Anjali, his mother and brother. [who I'm
only not calling by their name in this post as they deserve some privacy
and their Identities is not listed on Atuls wikipedia page].

Atul was 51 years old. Way too young to die. Yet, he has managed to
created a legacy that will extend long beyond his life. He profoundly
influenced generations of technology enthusiasts in India and beyond.

OsmoDevCon
2013 is getting closer every day, and I'm very much looking forward
to meet the fellow developers of the various Osmcoom sub-projects.
Organization-wise, the catering has now been sorted out, and Holger has
managed to get a test license for two ARFCN from the regulatory body
without any trouble.

This means that we're more or less all set. The key needs to be picked
up from IN-Berlin, and we need to bring some extra extension cords,
ethernet switch, power cords and other gear, but that's really only very
minor tasks.

There's not as much formal schedule as we used to have last year, which
is good as I hope it means we can focus on getting actual work done, as
opposed to spending most of the time updating one another about our
respective work and progress.

As usual, murphy's law dictates that problems will occur at the worst
possible moment. One of my servers in the data center died on March 20,
and it was the machine which hosts the majority of the free software
projects that I've created or am involved in. From people.netfilter.org
to OpenPCD and OpenEZX to gpl-violations.org and virtually all
osmocom.org sites and services.

Recovery was slow as there is no hot spare and none of my other
machines in the data center have backplanes for the old SCA-80 hard
disks that are in use by that particular machine. So we had to send the
disks to Berlin, wait until I'm back there, and then manually rsync
everything over to a different box in the data center.

To my big surprise, not many complaints reached me (and yes, my
personal and/or business e-mail was not affected in any way)

Recovery is complete now, and I'm looking forward to things getting back
to normal soon.

For the better part of a year, this blog has failed to provide you with
a lot of updates what I've been doing. This is somewhat relate to a
shift from doing freelance work on mainline / FOSS projects like the
Linux kernel.

In April 2011, Holger and I started a new company here in Berlin (sysmocom - systems for mobile communications
GmbH). This company, among other things, attempts to provide
products and services surrounding the various mobile communications
related FOSS projects, particularly OpenBSC, OsmoSGSN, OpenGGSN, but
also OsmocomBB, and now also OsmoBTS + OsmoPCU, two integral components
of our own BTS product called sysmoBTS.

Aside from the usual software development, this entails a variety of
other tasks, technical and non-technical. First of all, I did more
electrical engineering than I did in the years since Openmoko. And even
there, I was only leading the hardware architecture, and didn't actually
have to capture schematics or route PCBs myself. So now there are some
general-purpose and some customer-specific circuits that had to be done.
I really enjoy that work, sometimes even more than software development.
Particularly the early/initial design phase can be quite exciting.
Selecting components, figuring out how to interconnect them, whether you
can fit all of them together in the given amount of GPIOs and other
resource of your main CPU, etc. But then even the hand-soldering the
first couple of boards is fun, too.

Of all the things I so far had least exposure to is casing and
mechanical issues. Luckily we have a contractor working on that for us,
but still there are all kinds of issues that can go wrong, where
unpopulated PCB footprints can suddenly make contact with a case, or
all kinds of issues related to manufacturing tolerances. Another topic
is packaging. After all, you want the products to end up in the hands
of the customer in a neat, proper and form-fitting package.

On the other hand, there is a lot of administrative work. Sourcing
components can sometimes be a PITA, particularly if even distributors
like Digikey conspire against you and don't even carry those low
quantities of a component that we need for our 100-board low quantity
runs. EMC and other measurements for CE approval are a fun topic, too.
I've never been involved personally in those, and it has been an
interesting venture. Luckily, at least for sysmoBTS, things are looking
quite promising now. Customs paperwork, Import/Export related
buerocracy (both in Germany as well as other countries) always have new
surprises, despite me having experience in dealing with customs for
more than 10 years now.

Also significant amount of time is spent on evaluating suppliers and
their products, e.g. items like SIM/USIM cards, cavity duplexers,
antennas, cables, adapters, power amplifiers and other RF related
accessories for our products.

The thing that really caught me off-guard are the German laws on
inventory accounting. Basically there is no threshold for low-quantity
goods, so as a company on capital (GmbH/AG) you have to account for each
and every fscking SMD resistor or capacitor. And then you don't only
have to count all those parts, but also put a value at them. Depending
on the type of item, you have to use either the purchasing price, or the
current market price if you were to buy it again, or the price you
expect to sell the item for. Furthermore, the trade law requirements on
inventory accounting are different than the tax laws, not often with
contradictory aims ;)

In the end it seems the best possible strategy is to put a lot of the
low-value inventory into the garbage bin before the end of the financial
year, as the value of the product (e.g. 130 SMD resistors in 0402 worth
fractions of cents) is so much lower than the cost of counting it. Now
that's of course an environmental sin, especially if you consider lots
and lots of small and medium-sized companies ending up at that
conclusion :(

So all in all, this should give you somewhat of an explanation why there
might have been less activity on this blog about exciting technical
things. On the one hand, they might relate to customer related projects
which are of confidential nature. On the other hand, they might simply
be boring things like dealing with transport damage of cavity duplexers
from china, or with FedEx billing customs/import fees to the wrong
address...

Overall I still have the feeling that I was writing a decent amount of
code in 2012 - although there can never be enough :) Most of it was
probably either related to OsmoBTS, OpenBSC/OsmoNITB or the various
Erlang SS7/TCAP/MAP related projects. The list of more
community-oriented projects with long TODO lists is growing, though.
I'd like to work on SIMtrace MITM / card emulation support, the
CC32RS512 based smartcard OS, libosmosim (there's a first branch in
libosmocore.git). Let's hope I can find a bit more time for that kind
of stuff this year. You should never give up hope, they say ;)

As (almost) every year, I attended the annual incarnation of FOSDEM. It is undoubtedly (one of?) the most
remarkable events about Free Software in existence. No registration, no fees,
24 tracks in parallel, an estimated 5000 number of attendees. I also like that
it brings together people from so many different communities, not _just_ the Linux or Gnome or KDE or Telephony or Legal people, but a good mixture of everything.

I have to congratulate the organizers, who manage to pull this off, year after
year again. And as opposed to many other events, they do so quietly and
without much recognition, I feel. I'd also like to thank the many volunteers
working tirelessly before, at and after the event. Last, but not least, I'd
like to thank the local university (ULB Solbosch) hosting the event.

What made me truly sad though, is the amount of littering that surprisingly
many of the attendees did. This was particularly visible in the Cafeteria.
Imagine an event run by volunteers, who put in a lot of time and effort.
Imagine an event where food and drinks are sold by volunteers at such low
prices that there can barely be any profit at all. And then imagine people
eating there and leaving all their rubbish around, as if they were in some kind
of restaurant where they are being served and where somebody is cleaning up
after them. It really makes me feel very bitter to see this. Don't people
realize that those very volunteers who are creating the event will then have to
put in _their_ spare time just because those who just enjoyed their coffee or
lunch didn't have the extra 30 seconds of bringing their trash to the trashcan?
I feel ashamed for members of our community who behave this way. Please think
next time before acting and show your respect to the people behind FOSDEM.

The fact that I have more than 20 missed phone calls on my land line
telephone after only half a day has passed triggers me to write this
blog post.

It is simply impossible to get any productive work done if there
are synchronous interruptions. If I'm doing any even remotely complex
task such as analyzing code, designing electronics or whatever else,
then the interruption of the flow of thoughts, and the context switch to
whatever the phone call might be about is costing me an insurmountable
amount of my productive efficiency. I doubt that I am the only one
having that feeling / experience.

So why on earth does everybody think they are entitled to interrupt my
work at any given point in time they desire? Why do they think whatever
issue they have rectifies an immediate interruption in what I am doing?
To me, an unscheduled phone call almost always feels like an insult. It
is a severe intrusion into my work-flow, and has a very high cost to me
in terms of loss of productivity.

Sure, there are exceptional absolute emergencies (like, a medical
emergency of a family member). But just about anything else can be put
in an e-mail, which I can respond to at a time of my choosing, i.e. at a
time I am not deeply buried into some other task that requires expensive
context switching and the associated loss of productivity. And yes, a
response might be the same day, some days later, or even a week or more
later. There are literally hundreds of mails of dozens of people that
need to be responded to. I can never even remotely answer all of them
in a timely manner, even if I'm working 12-14 hours a day up to 7 days a
week.

Right now I'm doing the only reasonable thing that is left: Switch off
all phones. And to anyone out there intending to contact me: Please
think twice before calling me on the phone. Almost anything can be put
in an e-mail. And if you really want to have a phone call, please
request a scheduled phone call in an e-mail containing a very detailed
agenda and explanation of the topic.

From roughly September to December 2012 I seem to have had a quite
unusual strain of bad luck and set-backs. I don't want to go into the
details here, as most of the issues are of quite private nature.

This has kept me quite distracted from a lot of my other activity.
Projects like the various Osmocom sub-projects, gpl-violations.org are
in desperate need of attention, and I have severely neglected my
responsibilities in the Chaos Computer Club Berlin e.V. :(

I don't even want to talk about actual paid work, where customers also
had to put up with repeated schedule slips and lack of availability.

I let down friends and colleagues at a number of occasions, as I was
unable to keep up with anything that remotely resembles my typical work
schedule.

Last but not least, I regrettably have also not felt much of an urge to
write many blog posts here.

My sincere hope and expectation is that things are going to improve
quickly in 2013. At least most of issues from the last half year have
been resolved. Now I need to work through a considerable back-log of
work and find more time for my volunteer projects in the FOSS and hacker
worlds. However, this will need some time and I would like to ask for
some patience. I do intend to be up to speed with things just like
before.

In this spirit, I am looking forward to a productive and exciting
2013. Happy hacking und Viel Spass am Gerät

When I first heard that the annual CCC congress was moved to Hamburg, my
immediate reaction was: Fine, but I wouldn't want to be involved in it.
For the last 15 years I've been attending the CCC congress every year,
in most years as a speaker, and in many years in some (small)
contributing role, first in the team doing the video recordings, and in
the last couple of years setting up a GSM network. Contributing to an
event is easy if your home/lab is within 20minutes, so if you need
another strange cable/adapter/tool/whatever, you can just go and grab
it. Doing that at an event that's multiple hours of driving away, in a
new/unknown venue is an entirely different story. I have more than
enough stress already with (paid) work and the various FOSS projects
that I'm leading or involved in.

I have no interest in "just" attending the event. That never was a
primary reason for me. In all those years, I've probably attended an
average of one talk each year. The event for me was about being able to
contribute something actively.

Now, months after those thoughts and my decision not to attend, there is
a schedule for the 29C3 available. And to say the least, I am shocked.
The entire event seems to have turned into a SIGINT, rather than an
xxC3. Lots of talks on politics and society, and lots of German talks.

The debate on implications of technology on society, culture, politics,
etc. is an important debate, there is no doubt. And so far I always had
the feeling that the xxC3 had a pretty good balance between hard-core
technical talks and those non-technical talks. But if I look at the
schedule this year, it really looks like an incarnation of the SIGINT
conference. With too many German talks you are scaring off the
international community. And with focussing on non technical topics,
you scare away the die-hard technical hackers. So why move to a larger
venue, if you at the same time seem to limit the scope of the event?

Meanwhile I have heard of a number of friends and colleagues who seem to
share this view. A number of people who have attended in previous years
are not interested in attending this year due to the issues mentioned
above.

It's sad to see, but I somehow have the feeling that 29C3 might be the
end of an era. The end of a highly successful series of events with
exceptionally strong technical talks. To me, xxC3 has always been
unique and special. No other event would ever compare to it. Who will
fill the gap for the die-hard technical topics? I am feeling quite sad,
up to the point that I want to start mourning about "the good old
times".

I'm not writing this to put blame on anyone. It just reflects my
personal and highly subjective view. Let's see what people will say
after 29C3 has actually happened. Let's see how successful it is in
terms of number of attendees, and in terms of feedback from
participants.

In many cellular systems (GSM or otherwise) there is a frequency duplex
between the uplink and downlink frequency band. If you use a single
antenna to serve a BTS, then somehow you need to split the frequency
band between the Rx and Tx side by means of a Duplexer.

The most common technology for this is the so-called Cavity
Duplexer. I've used those devices (and seen them in use) for a long
time, but never really opened one so far. The problem is that they are
finely tuned, and each mechanical change can severely impact
performance. As I had to repair a broken SMA socket on one of them
recently, I took the chance to take a picture

In the first picture you can see the bottom side. This consists of a
milled aluminum block, with a series of circular cavities. The Tx
output of the BTS is connected to the SMA socket on the bottom right,
the antenna to the SMA socket on the top side, and the Rx port to the
SMA socket on the bottom left of the picture:

The small cylindrical objects in the center of the cavities are not
milled from the same part, but they are separate pieces mounted by
screws from the bottom of the unit.

The second picture shows the top section of the duplexer:

You can see a ~ 4mm aluminum plate with lots of (now empty) holes which
are for the ~ 117 screws with which the top plate is screwed against the
bottom part shown in the first picture.

The important part, however, are the screws that you can see sticking out
of the top part. Those are used for tuning and present "obstacles" in
the path of the waves as they pass through the cavities.

The big miracle for me is not that there are some resonances which build
up a filter, but that you can actually transfer as much as 100W of RF
power from the Tx input through to the antenna output.

It's already one week in the past, but I'm only now finding some time to
report on the first Osmocom User Group meeting in Bavaria.

All-in-all, there were 6 people attending, some people already known in
the community, but also two completely new faces, which is great.

Dieter gave us a tour of his large BTS equipment, including a
Nokia Ultrasite and an Ericsson RBS 2206. We had an introduction round
where the participants could get to know each other a bit. Finally, we
spoke about a variety of topics, from OsmocomBB to SIMtrace, SIM/SAT/STK
security, the CC32RS512 and of course OpenBSC and the sysmoBTS.

On the day after the meeting I also had the pleasure of attempting to
get the RBS2206 working with OpenBSC. Unfortunately there was no
success, but still a number of bugs in the OM2000 / RBS2000 code in
OpenBSC that had been found and fixed.

I'd like to thank Dieter Spaar for organizing and hosting the event,
taking care of the Bavarian sausage + cheese platter for lunch.